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responded proactively to pressing regulatory, legal, and scientific needs for objective application of available sci- ence and identification of priority research to inform exposure criteria. He assembled and served as one of the complementary experts who contributed to the Southall et al. (2007) criteria, and he guided the panel through that process into the present one.
It was a bold vision by Gentry, given the expansive and complex nature of the issues. Those of us involved from the start, and those who joined later, were perhaps unpre- pared for the challenges of this venture. Our scientific training teaches us that firm conclusions often require larger sample sizes than exist for nearly any of the topics considered. This work has taken us out of our comfort zone to provide informed assessments where decisions must be made before all desirable data are available. We recognized that decisions about the effects of noise will be made one way or another and that it is useful to have experts familiar with the science work together through a transparent process to develop reasonable recommenda- tions, acknowledging extensive uncertainty and research needed to address it. As in the field of human hearing, any such criteria are certain to be outdated as soon as they are published, criticized in opposing ways by differ- ent stakeholders, and ultimately revised through better information and new ways of thinking. It has taken tough skins, updated knowledge, and compromises among those involved to accept those realities and to recognize they are, in fact, the necessary elements and outcome of such an adaptive progression.
Here, and in the two papers from the reconvened panel (Southall et al., 2019a, 2021), we highlighted needed research to build on available data and continue to improve criteria. It will not be possible to fill all the data gaps in areas of hearing, auditory effects, behavioral effects, nonauditory physiological effects, or the inter- action of multiple stressors for populations. Strategic thinking is needed, with an emphasis on more compre- hensive data and larger sample sizes for “representative” species and integrating responses and vital life history parameters to consider longer term and potential popula- tion impacts (see Pirotta et al., 2021).
The collective recent efforts of the panel are subsequent steps in an evolving, self-correcting process that will continue into the future. The decade between Southall
et al. (2007) and the onset of the current efforts is prob- ably a realistic period for such reassessment given the pace of science and the enormity of the issues. Future efforts should build on the solid foundations of exper- tise, knowledge, and methods to date and bring new minds and new ideas to bear. Future criteria should consider potential significant population-level behavioral, masking, and physiological effects and perhaps other eco- system considerations yet to be identified.
Acknowledgments
This work would not have been possible without decades of almost entirely in-kind support by the scientists iden- tified in the Foreword. Travel and logistical support for different phases in the panel process were provided by the United States National Marine Fisheries Service, United States National Science Foundation, and the Joint Indus- try Program on Sound and Marine Life. The permitted use of images from Southall et al. (2019a) by Aquatic Mammals is appreciated.
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